Study On Flexural Behavior Of Layered Polyvinyl Alcohol Fiber Reinforced Concrete Beams

Concrete is the most widely used building material in social life today,but there are some shortcomings such as heavy weight,low tensile strength and easy to crack in concrete.Existing research and engineering practice have proved that incorporation of fiber is an effective means to improve the performance of concrete.The engineering application at home and abroad shows that PVA fiber reinforced concrete has excellent properties and broad application prospects.However,there are few studies on the structure of PVA fiber concrete in our country,and lack of technical support in practical engineering applications.In this paper,eleven layered PVA fiber reinforced concrete beams and one ordinary reinforced concrete beam bending test research,the main results of the study are as follows:(1)Through the tests of flexural strength of different kinds of fiber-reinforced concrete beams with different volume fraction of PVA fiber,it can be concluded that with the increase of PVA fiber volume fraction,the early crack resistance of concrete beams can be obviously improved,the cracking load increases,the deflection decreases and the ultimate bearing capacity no change.The crack load was increased by 18%,23.7%,30% and 34.3% respectively compared with the ordinary concrete beam when the fiber bundles were 0.05%,0.09%,0.15% and 0.2%,respectively.For example,the deflections of beams with different fiber volume fraction decrease by 6.7%,9.2%,17.6% and 20.2% respectively compared with that of ordinary concrete beams at an applied load of 20 kN.The ultimate load stratum fiber reinforced concrete beam and ordinary concrete beam is basically the same.(2)The test of flexural strength of RC beams with different thickness of PVA fiber layer shows that with the increase of PVA fiber layer thickness,the crack resistance of concrete beams is obviously improved,the cracking load is increased,the deflection value is reduced and the ultimate load does not occur Variety.Compared with the ordinary concrete beam,the cracking load of the test beam increased by 20.3%,23.8% and 28.7%,respectively,under the same conditions of other conditions,with the thickness of the fiber layer being 1 / 5h,1 / 3h and 1 / 2h.At an applied load of 20 kN,the deflection of the layered fiber reinforced concrete beam decreases by 2.5%,9.2% and 12.6% respectively compared with that of the ordinary concrete beam.The ultimate load stratum fiber reinforced concrete beam and ordinary concrete beam is basically the same.(3)Based on the calculation formula of cracking load of common reinforced concrete beam,this paper fits the calculation formula of cracking load which takes into account the thickness of fiber layer and fiber volume fraction,and the error between fitting value and actual value is in the range of-2.4%~2.1% The formula can approximate the cracking load of layered PVA fiber reinforced concrete beam.Based on the formula of maximum crack width of ordinary reinforced concrete beam,the formula of maximum crack width considering the thickness of fiber layer and fiber volume fraction is fitted.Compared with the actual value,the error is within the range of-5.8%~-1.7%,indicating that the fitting formula can approximate the maximum crack width of the layered PVA fiber reinforced concrete beam.